Spam and e-mail carrying malicious attachments (e.g., viruses, worms, etc.) are a serious computer security problem. Traditionally, senders of spam have obtained e-mail addresses by combing through web pages, bulletin boards, Usenet and the like. Addresses gleaned in this way were subsequently compiled, utilized for sending spam and/or sold to other spammers. Thus, once an e-mail address was posted in a publicly accessible location, the amount of spam sent to the e-mail address would typically increase rapidly.
As users and enterprises have become educated concerning best practices such as “munging” and spamtraps, these sources of addresses have diminished. As a result, spammers are now relying on new and more aggressive techniques for obtaining valid e-mail addresses. Today, savvy spammers prepare lists of e-mail addresses by sending out test spam messages to every conceivable user name at a target domain (a so called “dictionary attack”). The spammer then notes which e-mail messages reach their target recipient (and are thus valid addresses). To determine which e-mail messages reach their targets, the spammer can cull the bounces, monitor the logs of the transmitting server, and/or parse calls made to unique graphical beacons (e.g., small gif files) embedded in the test messages. Through this process, a spammer can assemble a list of e-mail addresses likely to be valid, and use the list to send out more spam (and/or sell the list to other senders of spam or other forms of malicious e-mail).
What is needed are computer implemented methods, computer readable media and computer systems for providing protection from spam and other malicious e-mail being sent to lists of e-mail addresses that are built in this manner.